Human Chorionic Gonadotropin (HCG)

Test Overview

The human chorionic gonadotropin (hCG) test is
done to check for the
hormone hCG in blood or urine. Some hCG tests measure
the exact amount and some just check to see if the hormone is present. HCG is
made by the
placenta during pregnancy. The hCG test can be used to
see if a woman is pregnant or as part of a screening test for birth
defects.

HCG may also be made abnormally by certain tumors,
especially those that come from an egg or sperm (germ cell tumors). HCG levels
are often tested in a woman who may have abnormal tissue growing in her uterus,
a
molar pregnancy, or a cancer in the uterus
(choriocarcinoma) rather than a normal pregnancy. Several hCG tests may be done
after a miscarriage to be sure a molar pregnancy is not present. In a man, hCG
levels may be measured to help see whether he has cancer of the
testicles.

HCG in pregnancy

An egg is normally fertilized by
a sperm cell in a
fallopian tube. Within 9 days after
fertilization, the fertilized egg moves down the
fallopian tube into the uterus and attaches (implants) to the uterine wall.
Once the fertilized egg implants, the developing placenta begins releasing hCG
into your blood. Some hCG also gets passed in your urine. HCG can be found in
the blood before the first missed menstrual period, as early as 6 days after
implantation.

HCG helps to maintain your pregnancy and affects the
development of your
baby (fetus). Levels of hCG increase steadily in the
first 14 to 16 weeks following your last menstrual period (LMP), peak around
the 14th week following your LMP, and then decrease gradually. The amount that
hCG increases early in pregnancy can give information about your pregnancy and
the health of your baby. Soon after delivery, hCG can no longer be found in
your blood.

More hCG is released in a multiple pregnancy, such as
twins or triplets, than in a single pregnancy. Less hCG is released if the
fertilized egg implants in a place other than the uterus, such as in a
fallopian tube. This is called an
ectopic pregnancy.

HCG blood tests

HCG blood tests can be used to see
if hCG is present but they can also measure the exact amount of hCG in the
blood. A blood test can be used to see if a woman is pregnant, to check for
abnormal pregnancies, or to test for hCG related to certain cancers.

The level of hCG in the blood is often used as part of a screening for
birth defects in a maternal serum triple or quadruple screening test. Generally
done between 15 and 20 weeks, these tests check the levels of three or four
substances in a pregnant woman's blood. The triple screen checks
alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and a type of
estrogen (unconjugated estriol, or uE3). The quad screen checks these
substances and the level of the hormone inhibin A. The levels of these
substances-along with a woman's age and other factors-help the doctor estimate
the chance that the baby may have certain problems or birth defects.

In some cases a combination of screening tests is done in the first
trimester to look for Down syndrome. This screening
test uses an ultrasound measurement of the thickness of the skin at the back of
the fetus's neck (nuchal translucency), plus a blood test of the levels of the
pregnancy hormone hCG and a protein called pregnancy-associated plasma protein
A (PAPP-A). This test is about as accurate as the second-trimester maternal
serum quad screening.1

HCG urine tests

HCG urine tests are usually used
for routine pregnancy testing. The test does not measure the exact amount of
hCG, but it shows if hCG is present. Home pregnancy tests that show hCG in
urine are also widely available.

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Why It Is Done

See whether there is an increased chance of birth defects such as
Down syndrome. The test is used in combination with other screening
tests.

Find and check the treatment of a cancer that develops from
an egg or sperm (germ cell cancer), such as cancer of the
ovaries or testicles. In such cases, a test for
alpha-fetoprotein may be done along with a test for hCG.

How To Prepare

If a blood sample is collected, you do
not need to do anything before you have this test.

If a urine test
is done, the first urine of the day is generally the best to use because it has
the highest level of hCG. A urine sample collected at least 4 hours after
the last urination will also have high amounts of hCG.

How It Is Done

Human chorionic gonadotropin (hCG) may
be measured in a sample of blood or urine.

Blood sample collection

The health professional
drawing blood will:

Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.

Clean the needle site with
alcohol.

Put the needle into the vein. If the needle is not placed
correctly or if the vein collapses, more than one needle stick may be
needed.

Attach a tube to the needle to fill it with
blood.

Remove the band from your arm when enough blood is
collected.

Put a gauze pad or cotton ball over the needle site as
the needle is removed.

Put pressure to the site and then a
bandage.

Urine collection

If possible, collect a sample
from the first urine of the day (this urine generally has the highest level of
hCG). A urine sample collected at least 4 hours after the last urination
will also have high amounts of hCG.

Place the collection container into the
stream of urine, and collect about
4 Tbsp (60 mL) of
urine.

Do not touch the rim of the container to your genital area,
and do not get toilet paper, pubic hair, stool (feces), blood, or other foreign
matter in the urine sample.

Finish urinating into the toilet or
urinal.

Carefully replace the lid on the container, and return it to
the lab. If you are collecting the urine at home and cannot get it to the lab
in an hour, refrigerate it.

How It Feels

Blood test

The blood sample is taken from a vein
in your arm. An elastic band is wrapped around your upper arm. It may feel
tight. You may feel nothing at all from the needle, or you may feel a quick
sting or pinch.

You may feel anxious while awaiting results of an
hCG test done to check the health of your baby.

Urine test

There is normally no discomfort with
collecting a urine sample.

Risks

Risks of a blood test

There is very little chance
of a problem from having a blood sample taken from a vein.

You may get a small bruise at the site. You can lower the
chance of bruising by keeping pressure on the site for several
minutes.

In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.

Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.

Urine test

There is no chance for problems while
collecting a urine sample.

Results

The human chorionic gonadotropin (hCG)
test is done to measure the amount of the
hormone hCG in blood or urine to see whether a woman
is pregnant. HCG may also be measured to see whether cancer of the ovaries or
testicles is present.

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

High values

If you are pregnant, very high levels of
human chorionic gonadotropin (hCG) can mean a multiple pregnancy (such as twins
or triplets), a
molar pregnancy,
Down syndrome, or that you are further along in an
early pregnancy than estimated by your last menstrual period
(LMP).

In a man or a nonpregnant woman, a high hCG level can mean a
tumor (cancerous or noncancerous) that develops from a sperm or egg cell (germ
cell tumor), such as a tumor of the testicles or ovaries, is present. It may
also mean some types of cancer, such as cancer of the stomach,
pancreas, large intestine, liver, or lung.

Low values

If you are pregnant, low levels of hCG can
mean an
ectopic pregnancy, death of your baby, or that you are
not as far along in an early pregnancy as estimated by your last menstrual
period (LMP).

If you are pregnant, levels of hCG that are
decreasing abnormally can mean a
miscarriage (spontaneous abortion) is very
likely.

What Affects the Test

Things that may affect the
results of your test include:

Doing a urine test for human chorionic
gonadotropin (hCG) very early in pregnancy (during the first week after
implantation) or on a urine sample taken in the middle of the day. The test may
not always show an early pregnancy.

Miscarriage (spontaneous abortion) or therapeutic abortion. HCG results may remain high
(positive) for up to 4 weeks after a miscarriage or
therapeutic abortion.

Getting an injection of hCG to treat
infertility. This may cause test results to appear high for several days after
the injection.

Having blood in the urine sample or soap in the
collecting container, which may change the hCG level.

Using
diuretics and promethazine. These
medicines can cause false low hCG levels in urine test results.

Using heparin, a medicine to prevent blood from
clotting (anticoagulant).

Using some medicines. These include hypnotics (such as Ambien),
antipsychotics, and antinausea medicines (such as prochlorperazine and
promethazine ). Be sure to tell your doctor what medicines you take.

What To Think About

Home pregnancy tests that find hCG in urine are
widely available. To learn more, see the topic
Home Pregnancy Tests.

A blood test for hCG
is generally more accurate than a urine test. If pregnancy is suspected even
after urine test results do not show a pregnancy (negative results), a blood
test can be done, or another urine test should be repeated in a
week.

HCG results may remain high (positive) for up to 4 weeks
after a miscarriage (spontaneous abortion) or therapeutic abortion.

A normal hCG value
does not rule out the possibility of a tumor in the uterus, ovaries, or
testicles. HCG is only one part of an overall evaluation when a tumor is
suspected.

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